Electric door opener

ABSTRACT

An electric door opener to be utilized in conjunction with a standard door closer or door check to provide the elements of automatic door control. The door opener is typically mounted on the transom of the door and includes an electric motor having a drive shaft that operates through a worm grear mechanism and an electromagnetic clutch to drive a gear train. The output of the gear train is operably connected to a linkage attached to the door. An approach switch, associated with an approach mat or a photoelectric eye, is located ahead of the door, while a safety switch is similarly associated with a safety mat or photoelectric eye located behind the door. With the closing of the approach switch by a pedestrian approaching the door, high voltage power is supplied to the motor and clutch to enable the motor to drive the gear train and pivot the linkage to move the door to the open position. In addition, closing of the approach switch will also supply low voltage power to the motor. When the door is in the full open position a limit switch is actuated which acts to remove high voltage power from the motor, leaving only low voltage power on the motor. The low voltage power supplied to the motor is sufficient to overcome the force of the door closer and maintain the door in the open position. A time delay is incorporated in the system which provides time for pedestrian movement from the approach mat to the safety mat, and to clear the safety mat before the door closes.

United States Patent [191 Boehm 1 ELECTRIC DOOR OPENER [75] Inventor:Raymond H. Boehm, Racine, Wis.

[73] Assignee: R. H. Boehm Company, Inc.,

Racine, Wis.

[22] Filed: Sept. 28, 1973 [21] Appl. No.: 401,841

Primary Examiner-Kenneth Downey Attorney, Agent, or FirmAndrus, Sceales,Starke & Sawall [57] ABSTRACT An electric door opener to be utilized inconjunction Apr. 1,1975

with a standard door closer or door check to provide the elements ofautomatic door control. The door opener is typically mounted on thetransom of the door and includes an electric motor having a drive shaftthat operates through a worm grear mechanism and an electromagneticclutch to drive a gear train. The output of the gear train is operablyconnected to a linkage attached to the door. An approach switch,associated with an approach mat or a photoelectric eye, is located aheadof the door, while a safety switch is similarly associated with a safetymat or photoelectric eye located behind the door. With the closing ofthe approach switch by a pedestrian approaching the door, high voltagepower is supplied to the motor and clutch to enable the motor to drivethe gear train and pivot the linkage to move the door to the openposition. In addition, closing of the approach switch will also supplylow voltage power to the motor. When the door is in the full openposition a limit switch is actuated which acts to remove high voltagepower from the motor, leaving only low voltage power on the motor. Thelow voltage power supplied to the motor is sufficient to overcome theforce of the door closer and maintain the door in the open position. Atime delay is incorporated in the system which provides time forpedestrian movement from the approach mat to the safety mat, and toclear the safety mat before the door closes.

15 Claims, 6 Drawing Figures PATENIEBAPR H975 SHEET 1 [IF 2 ELECTRICDOOR OPENER BACKGROUND OF THE INVENTION Automatic door operators arecommonly used in supermarkets, airports, department stores, and otherhigh volume traffic areas where pedestrians are burdened with packagesor luggage. Automatic door operators are normally installed in thetransom of the door, or alternately, under the floor, and are usuallyactuated by walk-on approach mats or a photoelectric eye. The automaticdoor operator performs the functions of opening the door, cushioning theopening action, stopping the opening action, closing the door andcushioning the door in the closed position. Automatic door operators arerelatively complex in structure, expensive to install and maintain, andrequire frequent maintenance by specially trained service personnel.

Door closers or door checks are commonly used in association withresidential, commercial or industrial doors. The conventional doorcloser provides opening speed control, opening cushioning, a stop forthe opening action, as well as providing closing power and closingcushion for the door. The conventional door closer is mounted externallyon the transom or on the door itself, and as the door is manuallyopened, the door closer stores energy to provide the closing power whenthe door is released. Conventional door closers are relativelyinexpensive, reliable and easy to install and maintain.

SUMNIARY OF THE INVENTION The invention relates to an electric dooropener to be utilized in conjunction with a standard door closer or doorcheck, together accomplishing automatic door operation with reliable,easy to install and maintain, relatively low cost elements. The electricdoor opener is typically mounted on the transom of the door and includesan electric motor having a drive shaft that operates through a worm geardrive and an electromagnetic clutch to drive a gear train. The outputofthe gear train is operably connected to a linkage attached to thedoor. An approach switch, which can take the form of a walk-on approachmat or a photoelectric eye, is located in front of the door and a safetyswitch, which can similarly take the form of a safety mat orphotoelectric eye, is located to the rear of the door. As a pedestriansteps on the approach mat, the approach switch is closed which acts toenergize the motor and the electromagnetic clutch to thereby drive thegear train and pivot the linkage to move the door to the open position.When the door is fully opened a limit switch is actuated which acts toremove the full power from the motor,

' leaving only low voltage power on the motor. The low voltage power issufficient to overcome the force of the door closer and maintain thedoor in the open position.

The door opener also includes a time delay which provides time for apedestrian to leave the approach mat and reach the safety mat before thedoor will begin to close. Through use of a variable resistor the timedelay can be selectively changed to suit the particular system.

The door opener of the invention is adapted to be used inconjunctionwith a standard door closer, and can be used with either newor existing doors. As the door opener does not include a mechanism forcontrolling closing of the door, the overall structure is simplified andthe cost is substantially reduced over that of conventional automaticdoor operators which provide both an opening and closing function.

The unit includes a symmetrical housing which can be directly installedon either right hand or left hand doors and can be utilized with eithercenter hung or butt hinged doors without modification to the opener orto the door.

The door opener of the invention also includes simple adjustments foropening speed of the door, time delay before closing, and direction ofoperation. The door opener also provides a power operated low voltageholding action to hold the door in the open position when a pedestrianis either on the approach or the safety mat, so that there is no dangerof overheating the motor under this hold-open condition.

DESCRIPTION OF THE DRAWINGS The drawings illustrate the best modepresently contemplated of carrying out the invention.

In the drawings:

FIG. 1 is a perspective view of the door opener of the invention asassociated with a door;

FIG. 2 is a vertical section of the door opener;

FIG. 3 is a horizontal section taken along line 3-3 of FIG. 2;

FIG. 4 is a section taken along line 44 of FIG. 2;

FIG. 5 is a section taken along line 5-5 of FIG. '2; and

FIG. 6 is a wiring diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a hingeddoorl which is mounted within a doorway defined by a frame 2. The frameincludes a pair of vertical jambs 3 which are connected at their upperends by a transom or lintel 4. A standard door closer or door check 5 isassociated with the door and can be a conventional hydraulic ormechanical type. The door closer 5 includes a housing 6 which is mountedon the transom and a pair of pivoting arms 7 are connected to the door.When the door is opened, energy will be stored by the door closer 5which will then act to return the door to the closed position in aconventional manner.

Door 1 is adapted to be opened by a door opener which is indicatedgenerally by 8 and is mounted on the transom 4. As best shown in FIG. 2,the door opener 8 includes an electrical control box 9 which containsthe electrical components of the system and lead wires 10 are connectedto the electrical components and are provided with a plug 11 which canbe engaged with a standard volt output. A three-conductor socket, notshown, is also furnished on the control box 9, to provide connections tothe approach mat and safety mat, the function of which will behereinafter described.

The door opener 8 also includes a permanent magnet motor 12, a worm gearreducing unit 13, a clutch assembly 14, and a gear box 15. To mount theopener on the transom 4, gear box 15 is provided with a pair of flanges16 which are connected by bolts 17 to the transom (FIG. 3).

As best shown in FIG. 5, the drive shaft 18 of motor 12 is connected tothe worm gear reduction unit 13 which includes a worm 19 which drivesgear 20 mounted on the upper end of vertical shaft 21. The

worm gear unit 13 not only provides a stage of reduction, but also willact to prevent the door from being slammed to the open position by agust of wind during the opening cycle.

The lower end of the shaft 21 is keyed to a hub 22 of the clutchassembly 14. The hub 22 is journalled for rotation within anon-rotatable annular electromagnetic core 23. The clutch assembly 14also includes an armature unit 24 including a central hub 25 and anouter ring 26. Ring 26 is normally spaced from the lower surface of thehub 22 to provide an air gap therebetween. The hub 25 of armature unit24 is connected to the upper end of a shaft 27 and a flat spring 28connects the hub 25 to the ring 26; When the core 23 is energized amagnetic field will be developed which will move the ring 26 upwardlyinto engagement with the hub 22, thereby bending the spring 28 upwardly,to provide a driving connection between the shaft 21 and the shaft 27.When core 23 is deenergized, the force of the deformed spring 28 willmove the ring 26 downwardly out of engagement with the hub 22 to therebydisconnect the shafts 21 and 27.

As illustrated in FIG. 2, the shaft 27 is journalled for rotation withinthe gear box 15 and carries a gear 29 which drives a gear 30 mounted onshaft 31, which is similarly journalled within the gear box 15. Shaft 31carries a small gear 32, which is engaged with a large gear 33 on shaft34, and shaft 34 also carries a small gear 35 which drives a gearsegment 36 mounted on the shaft 37. The lower end of shaft 37 projectsoutwardly of the gear box and is connected to one end of an arm 38. Theopposite end of arm 38 is pivotally attached to one end of an arm 39 andthe opposite end of arm 39 is pivotally connected to a clevis 40 that isattached by screws to the door 1. With this construction, rotation ofthe shaft 37 will cause the arms 38 and 39 to pivot to move the door tothe open position.

As shown in FIG. 2, a pin 42 is mounted within a central bore in theshaft 37 and pin 42 is provided with an enlarged head 43 that is locatedin a recess 44 in the end of the shaft 37. The upper end of the pin 42projects beyond the end of the shaft 37 and carries a cam 45. A pair ofBelleville springs 46 surround the pin 42 and provide frictional contactbetween the cam and the shaft 37 to restrict free rotation of the pinwithin the bore of the shaft. Cam 45 pivots with the shaft 37 and thearm 47 of a switch unit 48 rides against the peripheral surface of thecam 45. When the door is pivoted to the full open position the cam 45 isadapted to actuate the switch unit 48, as will be hereinafter described.

The door opener is adapted to be actuated by closing of anapproachswitch as a pedestrian approaches the door. As shown in FIG. 1, theapproach switch is associated with an approach mat 49 which is locatedon the floor in front of the door 1. As the pedestrian steps on theapproach mat 49, the approach switch is actuated to thereby operate thedoor opener. In addition to the approach switch, a safety switch isassociated with a safety mat 50 that is located on the floor behind thedoor. While the drawings illustrate the approach and safety switches tobe associated with mats, it is contemplated that various types ofswitches can be utilized, such as those actuated by photoelectric eyes,push bars, sonic actuation, or the like.

As shown in the wiring diagram, FIG. 6, 120 volt power from lines 51 and52 is supplied to the high voltage winding 53 of a transformer 54. Thepower lines 51 and 52 are also connected through lines 55 and 56 to fullwave bridge 57, the output of which is connected to coil 23 of theclutch assembly 14, and to full wave bridge 58, the output of which isconnected to the permanent magnet motor 12. Line 59 is connected acrosslines 55 and 56 and a variable resistor 60 and capacitor 61 areconnected in line 59. Line 62 connects line 59 with line 55 and solidstate switch unit 63 is connected in line 62 and serves to control thecurrent flow through line 55. Switch unit includes a diac 64, and atriac 65. The variable resistor 60 and capacitor 61 function as avoltage dividing network, and adjustment of resistor 60 will determinethe point in the half cycle in which the triac will fire and thusprovides a speed control for the motor.

Transformer 54 also includes a pair of low voltage windings 67 and 68,and in practice the winding 67 can be 28 volts while winding 68 is 14volts.

Lines 69 and 70 of a control circuit connect winding 67 to full wavebridge 71 and the command or approach switch 72 and the safety switch73, associated with approach mat 49 and safety mat 50, respectively, areconnected in parallel in line 69. The output of bridge 71 is connectedto relay 74 by lines 75 and 76, and capacitor 77 and a variable resistor78 are connected across line 75 and 76.

Lines 79 and 80 of a low voltage circuit connect the low voltage winding68 to full wave bridge 81, and the output of bridge 81 is connected tothe motor 12 by lines 82 and 83.

As the pedestrian walks on the approach mat 49, switch 72 closes and therelay 74 is energized. Energizing relay 74 will close the normally opencontacts 74-1, will open the normally closed contacts 74-2, will closethe normally open contact 74-3 in line 79 and will close the normallyopen contacts 74-4 in line 56. With the closing of contacts 74-4 powerwill then be supplied from the power lines 51 and 52 to the motor 12 andclutch coil 23 to operate the motor and engage the clutch. Closing ofcontacts 74-3 will serve to supply low voltage power to the motor thoughthe lines 79 and 80. Engagement of the clutch provides a drivingconnection between the motor 12 and the gear train to thereby pivot arms38 and 39 and move the door to the open position.

When the door moves to its fully opened position, the

the switch assembly 48. Limit switch 84 is connected in line 85, whichis connected between line 55 and line 59. With the closing of limitswitch 84 power will follow the path of least resistance through line85, thereby bypassing the switch unit 63 so that the supply of highvoltage power to the motor 12 will be terminated, since the triac isoff. The low voltage power being supplied through lines 79 and 80 to themotor will be sufficient to maintain the door in the open positionagainst the force exerted by the door closer 5. This situation, in whichlow voltage power is supplied to the motor 12, will continue to existwhile the approach switch 72 is closed.

If the pedestrian moves through the open door from approach mat 49 tothe safety mat 50, approach switch 72 will open, and the capacitor 77 isemployed to maintain energization of the relay 74 in the event theapproach switch 72 and safety switch 73 may both momentarily be open asthe pedestrian passes through the doorway. Capacitor 77 also provides atime delay when the pedestrian leaves the safety mat 50, or leaves theapproach mat 49 and does not step onto the safety mat 50, before thedoor will begin to close and permits the pedestrian to be safely out ofthe way of the door when it begins its closing action through operationof the door closer 5. Adjustment of the variable resistor 78, which istypically mounted on the control box 9, permits the duration of the timedelay to be selected for each installation.

When the pedestrian has stepped off of the safety mat 50, and there isno pedestrian on the approach mat 49, both the switches 72 and 73 willbe open, and after discharge of the capacitor 77 relay 74 will bedeenergized. Contacts 74-1, 74-3 and 74-4 will then open while contacts74-2 will close to shut off power to the motor 12 and to clutch coil 23and permit the closer 5 to return the door to the closed positionwithout torque.

being transmitted back through the motor.

The door opening logic can be illustrated by the equation:

where Q is the state of memory element (relay 74) and when Q l the relayis energized and when Q 0 the relay is deenergized; n is a state of timeand n l is the next state of time; A is the approach mat switch and A 1when the switch is closed and A 0 when the switch is open; S is thesafety mat switch and S 1 when the switch is closed and S 0 when theswitch is open.

Using the above equation, the following table of conditions can bedetermined:

Thus, the next state of the relay 74 (0, is deenergized if A and S are0, is equal to the existing state if S is 1 and A is 0 or 1, and isenergized if A is l and S is 0.

The door opener of the invention is adapted to be used in conjunctionwith a standard door closer and may be associated with any new orexisting door. It can be mounted on the door and is symmetrical forinstallation in either left hand or right hand doors. The door openercan be utilized with any type of contact closure, such as walk-on floormats, photoelectric eyes, pushbars, or the like.

The door opener includes simple adjustment for the opening speed throughoperation of the variable resistor 60 and for the time delay throughoperation of variable resistor 78.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. An electric door opener to be operably connected to a door to openthe same, comprising a unidirectional electric motor having an outputshaft, a worm gear unit connected to said output shaft, gear meanshaving an input and an output, electromagnetic clutch meansinterconnecting the worm gear unit and the input of the gear means, saidclutch means having an engaged and a disengaged position, a pivotablelinkage connecting the output of the gear means to the door, operationof said gear means acting to pivot the door through said linkage to anopen position, approach switch means located ahead of the door anddisposed to be actuated by a person approaching the door, meansresponsive to actuation of said approach switch means for engaging saidclutch means and for supplying the combination of high voltage power andlow voltage power to said motor, deactivation of said approach switchmeans curtailing the supply of power to said motor and disengaging saidclutch means, and limit switch means responsive to opening of the doorto a predetermined position for withdrawing the high voltage power andmaintaining the supply of low voltage power to said motor whereby thelow voltage power will retain the door in the open position.

2. The door opener of claim 1, and including time delay means fordelaying the curtailing of power to said motor and the disengagement ofsaid clutch means for a predetermined time after deactuation of saidapproach switch means. I

3. The door opener of claim 2, and including safety switch means locatedbehind the door and disposed to be actuated by a person located behindthe door, and means responsive to actuation of said safety switch meansfor engaging said clutch means and for supplying the combination of highvoltage and low voltage power to said motor, so that the door will bemaintained in the open position while said safety switch means isactuated.

4. The door opener of claim 2, and including means operably connected tosaid time delay means for selectively varying said predetermined time.

5. The door opener of claim 4, and including means responsive toactuation of said approach switch means and said safety switch means forpreventing opening of said door.

6. In combination, a door to enclose a doorway and movable between anopen and a closed position; a door closer having a force operating tomove the door from the open to the closed position; and a door openerseparate from said door closer to move the door from the closed to theopen position; .said door opener compris ing a uni-directional electricmotor having anoutp'ut shaft, a worm gear unit connected to said outputshaft, gear means having an input and an output, electromagnetic clutchmeans interconnecting the worm gear unit and the input of the gearmeans, said clutch means having an engaged and a disengaged position, apivotable linkage connecting the output of the gear means to the door,operation of said gear means acting to pivot the door through saidlinkage to an open position, approach switch means located ahead of thedoor and disposed to be actuated by a person approaching the door, meansresponsive to actuation of said approach switch means for engaging saidclutch means and for supplying the combination of high voltage power andlow voltage power to said motor, deactivation of said approach switchmeans curtailing the supply of power to said motor and disengaging saidclutch means, and limit switch means responsive to opening of the doorto a predetermined position for withdrawing the high voltage power, saidlow voltage power being sufficient to overcome the closing force of thedoor closer to thereby maintain the door in the open position untildeactivation of said approach switch means.

7. The combination of claim 6, wherein said approach switch means isassociated with a walk-on floor mat.

8. The combination of claim 6, and including safety switch means locatedbehind the door and disposed to be actuated by a person located behindthe door, and means responsive to actuation of said safety switch meansfor engaging said clutch means and for supplying the combination of highvoltage power and low voltage power to said motor, so that the door willbe maintained in the open position while said safety swtich means isactuated.

9. The combination of claim 8, wherein said safety switch means isassociated with a walk-on floor mat.

10. The combination of claim 6, and including time delay means fordelaying the curtailing of power to said motor and the disengagement ofsaid clutch means for a predetermined time after deactuation of saidapproach switch means.

ll. ln combination, a door to enclose a doorway and movable between anopen and a closed position; a door closer to move the door from the opento the closed position, and a door opener to move the door from theclosed to the open position, said door opener comprising an electricmotor having an output shaft, a worm gear unit connected to said outputshaft, gear means having an input and output, electromagnetic clutchmeans interconnecting the worm gear unit and the input of the gearmeans, said clutch means having an engaged and a disengaged position, apivotal linkage connecting the output of the gear means to the door,operation of said gear means acting to pivot the door through saidlinkage to an open position, a first electrical circuit connected to asource of high voltage power,

' a transformer having a high voltage winding connected in said circuitand having a pair of low voltage windings, an approach switch locatedahead of the door and disposed to be closed by a person approaching thedoor, a safety switch located behind the door and disposed to be closedby a person being in a position behind the door, a second electricalcircuit connected to a first of said low voltage windings, said approachswitch and said safety switch being connected in parallel in said secondcircuit, a relay connected in said second circuit and having a pluralityof contacts, whereby closing of said approach switch or said safetyswitch will energize the relay to actuate said relay contacts, a thirdelectrical circuit connected to the source of high voltage power, saidmotor and said clutch means and a first of said contacts being connectedin series in said third electrical circuit whereby closing of said firstcontact through energization of said relay will operate said motor andengage said clutch means, a fourth electrical circuit connecting thesecond low voltage winding to said motor, a second of said contactsbeing connected in series with said motor in said fourth circuit,whereby energizing of the relay will close said second contact tothereby supply low voltage power to said motor, and a limit switchdisposed to be actuated when the door is opened to a predeterminedposition and connected in the third circuit, actuating of the limitswitch will open the third circuit to cut off the supply of high voltagepower to the motor, whereby the low voltage power supplied to the motorthrough said fourth circuit will retain the door in the open position.

12. The combination of claim 11, and including a capacitor connected inparallel with said relay in said second circuit, the discharge of saidcapacitor acting after opening of said approach switch means and saidsafety switch means to continue energization of said relay for apredetermined period of time.

13. The combination of claim 12, and including a variable resistancedisposed in parallel with said relay and said capacitor in said secondcircuit, adjustment of said variable resistance acting to adjust thepredetermined period of time.

14. The combination of claim 11, wherein a solid state switch unit isconnected in said third circuit, said switch unit includes a triac and adiac, said limit switch being connected in said third circuit in amanner such that closing of said limit switch will bypass firing voltageto said switch unit and prevent firing of said triac to thereby cut offthe supply of high voltage power to the motor.

15. The combination of claim 14, and including voltage dividing meansconnected across said third circuit and including variable resistancemeans and a capacitor, said voltage dividing means arranged to set thevoltage at which the triac fires to thereby vary the magnitude of thehigh voltage power supplied to the motor.

1. An electric door opener to be operably connected to a door to openthe same, comprising a uni-directional electric motor having an outputshaft, a worm gear unit connected to said output shaft, gear meanshaving an input and an output, electromagnetic clutch meansinterconnecting the worm gear unit and the input of the gear means, saidclutch means having an engaged and a disengaged position, a pivotablelinkage connecting the output of the gear means to the door, operationof said gear means acting to pivot the door through said linkage to anopen position, approach switch means located ahead of the door anddisposed to be actuated by a person approaching the door, meansresponsive to actuation of said approach switch means for engaging saidclutch means and for supplying the combination of high voltage power andlow voltage power to said motor, deactivation of said approach switchmeans curtailing the supply of power to said motor and disengaging saidclutch means, and limit switch means responsive to opening of the doorto a predetermined position for withdrawing the high voltage power andmaintaining the supply of low voltage power to said motor whereby thelow voltage power will retain the door in the open position.
 2. The dooropener of claim 1, and including time delay means for delaying thecurtailing of power to said motor and the disengagement of said clutchmeans for a predetermined time after deactuation of said approach switchmeans.
 3. The door opener of claim 2, and including safety switch meanslocated behind the door and disposed to be actuated by a person locatedbehind the door, and means responsive to actuation of said safety switchmeans for engaging said clutch means and for supplying the coMbinationof high voltage and low voltage power to said motor, so that the doorwill be maintained in the open position while said safety switch meansis actuated.
 4. The door opener of claim 2, and including means operablyconnected to said time delay means for selectively varying saidpredetermined time.
 5. The door opener of claim 4, and including meansresponsive to actuation of said approach switch means and said safetyswitch means for preventing opening of said door.
 6. In combination, adoor to enclose a doorway and movable between an open and a closedposition; a door closer having a force operating to move the door fromthe open to the closed position; and a door opener separate from saiddoor closer to move the door from the closed to the open position; saiddoor opener comprising a uni-directional electric motor having an outputshaft, a worm gear unit connected to said output shaft, gear meanshaving an input and an output, electromagnetic clutch meansinterconnecting the worm gear unit and the input of the gear means, saidclutch means having an engaged and a disengaged position, a pivotablelinkage connecting the output of the gear means to the door, operationof said gear means acting to pivot the door through said linkage to anopen position, approach switch means located ahead of the door anddisposed to be actuated by a person approaching the door, meansresponsive to actuation of said approach switch means for engaging saidclutch means and for supplying the combination of high voltage power andlow voltage power to said motor, deactivation of said approach switchmeans curtailing the supply of power to said motor and disengaging saidclutch means, and limit switch means responsive to opening of the doorto a predetermined position for withdrawing the high voltage power, saidlow voltage power being sufficient to overcome the closing force of thedoor closer to thereby maintain the door in the open position untildeactivation of said approach switch means.
 7. The combination of claim6, wherein said approach switch means is associated with a walk-on floormat.
 8. The combination of claim 6, and including safety switch meanslocated behind the door and disposed to be actuated by a person locatedbehind the door, and means responsive to actuation of said safety switchmeans for engaging said clutch means and for supplying the combinationof high voltage power and low voltage power to said motor, so that thedoor will be maintained in the open position while said safety swtichmeans is actuated.
 9. The combination of claim 8, wherein said safetyswitch means is associated with a walk-on floor mat.
 10. The combinationof claim 6, and including time delay means for delaying the curtailingof power to said motor and the disengagement of said clutch means for apredetermined time after deactuation of said approach switch means. 11.In combination, a door to enclose a doorway and movable between an openand a closed position; a door closer to move the door from the open tothe closed position, and a door opener to move the door from the closedto the open position, said door opener comprising an electric motorhaving an output shaft, a worm gear unit connected to said output shaft,gear means having an input and output, electromagnetic clutch meansinterconnecting the worm gear unit and the input of the gear means, saidclutch means having an engaged and a disengaged position, a pivotallinkage connecting the output of the gear means to the door, operationof said gear means acting to pivot the door through said linkage to anopen position, a first electrical circuit connected to a source of highvoltage power, a transformer having a high voltage winding connected insaid circuit and having a pair of low voltage windings, an approachswitch located ahead of the door and disposed to be closed by a personapproaching the door, a safety switch located behind the door anddisposed to be closed by a person being in a position behind the door, asecond electrical circuit connected to a first of said low voltagewindings, said approach switch and said safety switch being connected inparallel in said second circuit, a relay connected in said secondcircuit and having a plurality of contacts, whereby closing of saidapproach switch or said safety switch will energize the relay to actuatesaid relay contacts, a third electrical circuit connected to the sourceof high voltage power, said motor and said clutch means and a first ofsaid contacts being connected in series in said third electrical circuitwhereby closing of said first contact through energization of said relaywill operate said motor and engage said clutch means, a fourthelectrical circuit connecting the second low voltage winding to saidmotor, a second of said contacts being connected in series with saidmotor in said fourth circuit, whereby energizing of the relay will closesaid second contact to thereby supply low voltage power to said motor,and a limit switch disposed to be actuated when the door is opened to apredetermined position and connected in the third circuit, actuating ofthe limit switch will open the third circuit to cut off the supply ofhigh voltage power to the motor, whereby the low voltage power suppliedto the motor through said fourth circuit will retain the door in theopen position.
 12. The combination of claim 11, and including acapacitor connected in parallel with said relay in said second circuit,the discharge of said capacitor acting after opening of said approachswitch means and said safety switch means to continue energization ofsaid relay for a predetermined period of time.
 13. The combination ofclaim 12, and including a variable resistance disposed in parallel withsaid relay and said capacitor in said second circuit, adjustment of saidvariable resistance acting to adjust the predetermined period of time.14. The combination of claim 11, wherein a solid state switch unit isconnected in said third circuit, said switch unit includes a triac and adiac, said limit switch being connected in said third circuit in amanner such that closing of said limit switch will bypass firing voltageto said switch unit and prevent firing of said triac to thereby cut offthe supply of high voltage power to the motor.
 15. The combination ofclaim 14, and including voltage dividing means connected across saidthird circuit and including variable resistance means and a capacitor,said voltage dividing means arranged to set the voltage at which thetriac fires to thereby vary the magnitude of the high voltage powersupplied to the motor.